Follow the below steps to create a Magento 2 module – PHPcodez_First

Step 1: Create the folder for the module
Step 2: Create etc/module.xml file
Step 3: Create etc/registration.php file
Step 4: Enable the module

Step 1: Create the folder of Hello World module

Name of the module is defined as “VendorName_ModuleName”. First part is name of the vendor and last part is name of the module. Focus on following guide to create the folders:
app/code/PHPcodez/First

Step 2: Create etc/module.xml file.

Then, it is necessary to create etc folder and add the module.xml file
app/code/PHPcodez/First/etc/module.xml

<?xml version="1.0"?>
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
  <module name="PHPcodez_First" setup_version="1.0.0">
  </module>
 </config>

Step 3: Create etc/registration.php file

In this step, we will add registration.php as following guide:
app/code/PHPcodez/First/registration.php

<?php
 \Magento\Framework\Component\ComponentRegistrar::register( \Magento\Framework\Component\ComponentRegistrar::MODULE,
  'PHPCodez_First',
  __DIR__
 );

Step 4: Enable the module

When step 3 is done , we have already created the First module. Now we should enable this module by running the following command.

php bin/magento module:enable PHPCodez_First

Now we should upgrade Magento database by running the following command.

php bin/magento setup:upgrade

After this we should deploy the static content

php bin/magento setup:static-content:deploy

Once deployment is done, you can also see your module from backend at Store -> Configuration -> Advanced -> Disable Modules Output.

Now, we will create a controller to test the module and for that we should create a route for this module.
Routes in Magento are divided into 3 parts: Route frontname, controller and action as following

example:
http://phpcodez.com/index.php/frontname/controller/action
To add route, it is necessary to create routes.xml file
app/code/PHPCodez/First/etc/frontend/routes.xml
since this is a frontend route, we added it in frontend/ folder else we need to add it to adminhtml/ folder

<?xml version="1.0" ?>
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:App/etc/routes.xsd">
  <router id="standard">
  <route frontName="first" id=" first ">
  <module name="PHPCodez_First "/>
  </route>
  </router>
 </config>

Now we will continue with the controller and action

The folder and file you need to create is: app/code/PHPCodez/First/Controller/Index/First.php

<?php
 namespace PHPCodez\First\Controller\Index;
 class Test extends \Magento\Framework\App\Action\Action
 {
  protected $_pageFactory;

public function __construct(
  \Magento\Framework\App\Action\Context $context,
  \Magento\Framework\View\Result\PageFactory $pageFactory)
  {
  $this->_pageFactory = $pageFactory;
  return parent::__construct($context);
  }

public function execute()
  {
  echo " PHPCodez - Your First Module Is Ready. Cheers !!! ";
  exit;
  }
 }

Once its done, please run php bin/magento cache:clean to check result.

Your URL now should be as http://phpcodez/first/index/first

Now the message ‘PHPCodez – Your First Module Is Ready. Cheers !!!’ will be displayed on the browser